ABSTRACT
This chapter deals with the environmental problems associated with the discharge of inadequately treated wastewater. It provides the reasons for treating wastewater and the classification and selection of treatment processes. The chapter describes the ultimate disposal of treated wastewater, including "dilution" and discharge to surface water such as rivers, lakes, reservoirs, and estuaries. The theoretical model for analysis assumes complete mixing conditions, constant flow rates, and biodegradation of the pollutant follows the first-order reaction. Population equivalent of sewage or wastewater refers to a certain quality parameter — example, biochemical oxygen demand or suspended solids — as a per capita contribution, compared to some quality parameter of the per capita contribution of a standard sewage. The National Research Council formula is based on wastewater treatment plants in US military installations. Waste stabilization ponds are shallow earthen basins with a controlled shape or a natural depression that receives wastewater and retains it so that biological processes can proceed at acceptable levels.
